That could be the understatement of the year, if not the last 45 years, which is how long it’s been since Smith’s name was first etched onto the Adidas shoe.

For Smith, 70, the simple white leather sneaker with a colorful heel and perforated sides has made him more of a household name than the game of tennis ever did, despite having once been the best American player and winner of the 1971 U.S. Open and 1972 Wimbledon tournaments.

The Adidas silhouette, created by Horst Dassler, the son of company founder Adi, debuted in 1965 as the first leather tennis shoe and had French pro Robert Haillet’s name on it. But when the German company aimed for a stronger U.S. presence, it turned to Smith.

The athletic label signed him to his first five-year deal, planted his face on the shoe’s tongue and left Haillet’s autograph on the side. By 1978, Smith had it all to himself. (His current endorsement deal ends in 2018. He and longtime agent Donald Dell are in negotiations with Adidas to renew.)

Adidas Stan SmithCourtesy

“The autograph was interesting because I was signing my name in the early ’70s when a girl I was dating thought it was boring and suggested I use just an S,” said Smith. “I thought that was original. Then I got married, and it felt funny to use the S, so I started signing ‘Stan Smith’ again.”

Since then, the shoe’s look hasn’t changed much, except for a higher heel that adds Achilles support and a loop up front to keep the tongue from sliding. What has changed, though, is the fan base.

In the early 2000s, the style’s sleek, clean looks and affordable prices caught on with the fashion crowd. It also didn’t hurt that Jay-Z rapped about Stan Smiths in 2001, and then in 2013, Gisele Bundchen posed nude in them for Vogue.

“The shoe is timeless. The styling is quite simple but very distinctive. It’s a recognizable shoe, and people gravitate to it because of its simplicity,” said Matt Powell, sports industry analyst at The NPD Group Inc. “This is a shoe for everyone. It was originally a performance shoe, but most people didn’t wear it for its intended purpose. It’s an asexual, gender-free shoe that also appeals to both young and old.”

What’s more, Adidas has handled this asset masterfully. The company took the shoe off the market in 2012 — Smith wasn’t happy with that decision at the time — largely because the style was showing up in discount bins. Within two years, Adidas executives relaunched it with savvier marketing, new colors and materials, and cool collaborations with the likes of Pharrell.

“The shoe serves as the perfect billboard space for all kinds of different textures and to message things,” said the music star.

“In addition to being iconic, Adidas has done a good job of pulsing it in and out of the market appropriately,” said Dick Johnson, chairman, president and CEO of Foot Locker Inc. “The shoe has been incredibly hot, and they’ve been able to consistently introduce it to a new generation of sneaker lovers. Whenever there’s a new iteration, they get the past consumers who loved it and new people. They have the ability to sell to men and women, and have a multigenerational impact.”

For Smith, his gig with Adidas is just one facet of a busy so-called retirement. In addition to making dozens of personal appearances for the athletic brand, the grandfather of 12 also serves as president of the International Tennis Hall of Fame, runs a tennis academy with Billy Stearns in Hilton Head, S.C., and has his own corporate events business.

The tennis legend told FN that much of his good fortune comes from lucky timing, but he is optimistic that even more positive things will come from his work with Adidas.

“The shoe is widely bought around the world, and my hope is that it could be looked at as a unifying factor, a commonality of people around the world,” Smith said. “People are more alike than they are different. If everyone could realize that, ultimately we could get more people to be peaceful toward different cultures, backgrounds, languages.”